Hard disk drive systems, also called Winchester drives, have one or more rigid disks rotatably mounted inside a case or "clean chamber" sealed to keep out dust and other foreign matter. Hard disk drives, in contrast to floppy disk drives, are characterized by their high storage capacity and speed of access to stored information.
For several reasons, it is desirable to provide for the removability of the disks by the computer user, and to permit the disks to be interchangeable between computer systems. For one thing, the security of the stored information can be better preserved. Removable and interchangeable hard disks can also serve as backup memories with storage capacities and access speeds unattainable with floppy disks or magnetic tapes.
One approach to hard disk removability and interchangeability is the hard disk cartridge. The disk is enclosed within a housing which, when the cartridge is installed, provides access for the disk drive spindle and read/write head assemblies. Conceptually, this approach resembles that of the floppy disk drive. However, because these hard disk cartridge systems do not have sealed disk chambers and due to handling of the cartridge, the disks and read/write heads are often exposed to unacceptable levels of contamination. Moreover, because the disk is removably coupled to the drive spindle, the required precise, reproducible centering and positioning of the disk relative to the head carriage assembly are difficult to achieve.
U.S. Pat. Nos. 3,849,800 and 4,034,411, issued to IBM, and IBM Technical Disclosure Bulletin, Volume 20, No. 10, March 1978, pp. 4104-05, disclose removable and interchangeable disk file modules which are sealed and enclose the disk and the head carriage assembly. The disk is mounted on a spindle one end of which projects from the module for coupling to a drive motor. These removable disk files do not incorporate components such as the spindle drive motor and therefore require both mechanical and electrical connections with the remainder of the computer system.
U.S. Pat. No. 4,062,049, issued to Burroughs Corporation on Dec. 6, 1977, discloses a self-contained, replaceable and interchangeable "disk file module" requiring only an electrical connector and no external mechanical couplings. The disk file of U.S. Pat. No. 4,062,049, among other drawbacks, is a relatively large, heavy unit utilizing 14-inch disks, is inserted and withdrawn from a mounting rack manually and may be removed while the disk drive is in operation.